“The question is can a federal agent assist in state criminal issues.”
Please name the crime, state or federal.
And given there’s been no extradition request, the idea that the federal government should interject itself in a political squabble is bizarre.
This is one federal law that could apply:
https://en.wikipedia.org/wiki/Assimilative_Crimes_Act
However I agree with other posters that when someone violates state law and then flees the state that the FBI has the authority to pursue and detain them.
AND again, I did not state an extradition request has been made, you do realize you cannot make such a request until someone is at least confirmed to be within your borders through some legally recognized means? More often that means within the state’s custody.
Unless you can actually start asking and talking with some sense I am not furthering anymore replies to your rants.